Conventionally, various pharmaceutical dosage forms for oral administration are known. However, there are few dosage forms with consideration for easy ingestion for patients, and especially dosage forms that are suitable for aged individuals, children and seriously ill patients, who are likely to accompany difficulty in the ingestion of the dosage forms, are desired. For example, tablets and capsules are most commonly used dosage forms, from the viewpoint of its ability of dosing given amounts or physicochemical stability, and further from the viewpoint of production costs; on the other hand, many patients disfavor from ingesting the tablets and capsules, because of the reasons such as the tablets and capsules are less likely to be easily ingested, but caught at the throat. Powders and granules are more difficult to be swallowed, but remain in the oral cavity, thereby giving a lingering unpleasant after-taste in the mouth. Solutions such as syrups are considered to be dosage forms that are suitable for aged individuals and children; the ingestion of liquids by volumetric measurements accompanies difficulties for aged individuals, children and seriously ill patients, so that ingestion in an accurate amount cannot be expected. In addition, the liquids yet had some problems with physicochemical stability. In recent years, many techniques relating to formulations quickly disintegrating in the oral cavity are disclosed in the dosage forms having both maintenance of ability of dosing given amounts and physicochemical stability owned by the tablets and capsules and easy ingestion as in syrups (Patent Publications 1, 2, 3, and 4).
However, the above techniques have various problems in that a relatively large amount of water is used, so that the drug is more likely to be unstable, that the formulation does not have an appropriate strength so that there is a risk of being damaged in the process of distribution, and further that an impediment in tableting, such as sticking or capping, is caused upon tableting during the production process in tableting, thereby showing difficulty in handling the formulation.
Various combinations of additives and production methods have been studied in order to solve the above problems; however, a production method, for example, a method of drying tablets under humidification after molding, an external lubrication method, or the like is complicated, so that specialized apparatuses are necessitated in many cases.
Relatively commonly used techniques include those in Patent Publication 5, Patent Publication 6, and the like, and in any of these techniques, further studies must be made in order to provide an oral disintegrating tablet that shows fast disintegrating ability in the oral cavity and has an appropriate strength, and that does not dependent on a specialized production method.
Patent Publication 7 discloses a tablet not only showing a fast disintegrating ability and excellent feel upon ingestion in the oral cavity, but also having an appropriate strength so that the tablet does not breakdown in the process of distribution. In addition, Patent Publication 8 discloses a tablet that rapidly degrades (disintegrates) in the mouth, using a soluble diluent used in the form of a directly compressible formed product.
On the other hand, in the recent medical field work, even an oral disintegrating tablet is desired to have a high tablet strength, so that it is desired not only to prevent damages such as cracks and defects upon taking the tablet out from PTP (blister) packaging, but also to enable packaging by an automatic tablet packaging machine.    Patent Publication 1: Japanese Patent Laid-Open No. Hei 9-309821    Patent Publication 2: Japanese Patent Laid-Open No. Hei 9-309822    Patent Publication 3: WO 93/12769    Patent Publication 4: Japanese Unexamined Patent Publication No. Hei 7-501829    Patent Publication 5: Japanese Unexamined Patent Publication No. Hei 10-182436    Patent Publication 6: Japanese Patent Laid-Open No. Hei 9-71523    Patent Publication 7: WO 00/47233    Patent Publication 8: Japanese Patent Laid-Open No. Hei 11-35450